The present invention relates generally to security apparatus for information processing systems, and more particularly to a system for providing controlled access to information signals in a point-to-point communication system that shares a common communication path.
In point-to-point communication systems, transmissions must be secured so that parties other than the one for which the transmission is intended cannot intercept or decode the transmission. There are many schemes available for controlling access to electronic signals, such as in the cable television environment. Other applications in which security schemes are required are broadband telephony systems, broadband multimedia systems and broadband video on demand systems.
Typically, a system subscriber is provided with a decoder connected between a signal source (e.g., cable television feed or satellite television receiver) and an output device such as a television set, video recorder, personal computer, or the like. Each subscriber's decoder is remotely accessed by the system operator to enable or disable the receipt of specific services such as the Home Box Office (HBO) movie channel or special pay-per-view sports events. In the past, distribution of such premium services (i.e., services which require a recipient to pay an additional fee) have been distributed to a plurality of subscribers at the same time. This was necessary because existing technology required a particular movie, for example, to be broadcast at a specific time for viewing by any authorized viewer that wanted to receive it. Thus, any subscriber that wanted to see a particular movie was required to tune into the movie at the scheduled time.
Technology now exists to enable the provision of information services, such as movies, special events, data services or the like, on demand. In such systems, point-to-point virtual connections are established between a "headend" or "central office" and an individual subscriber to enable the subscriber to view, e.g., a movie or special event at whatever time the subscriber desires. As with past distribution systems in which individual programs were broadcast according to a predefined schedule, the new point-to-point systems require security measures to prevent freeloaders ("pirates") from intercepting the signals and obtaining them without paying the required fee. Security measures are also necessary to prevent the privacy of a legitimate user from being violated. Even with security measures in place, pirates may attempt to break the system security and sell "black boxes" that enable the unauthorized reception of programming and data. It has been difficult and expensive for system operators to contend with the piracy problem.
Various systems have been designed to make piracy more difficult in the broadcast environment, where a plurality of subscribers are all receiving the same premium services at the same time. One such system is disclosed in U.S. Pat. No. 4,613,901 to Gilhousen, et al. entitled "Signal Encryption and Distribution System for Controlling Scrambling and Selective Remote Descrambling of Television Signals." In the Gilhousen, et al. scheme, various cryptographic keys are used to provide an encrypted television signal. Among the keys described are category keys, each common to a different subset of subscriber decoders. It is also known to provide program keys, in which each television program has a specific key associated therewith that is necessary to descramble or decrypt the particular program signal.
U.S. Pat. No. 5,115,467 to Esserman, et al. entitled "Signal Encryption Apparatus for Generating Common and Distinct Keys" also deals with the security issue. The generation of various different types of keys and their use is disclosed in the patent.
Encryption systems have been used in point-to-point systems for securing transmitted signals from unauthorized reception. In such methods, the data is coded such that parties without the appropriate "session key" are not able to decipher the transmission. When such a scheme is used in a shared media environment, it has required the dissemination of session keys prior to the establishment of each session. Session keys must be held in the utmost confidence as their compromise represents an opportunity for illegitimate parties to receive a transmission which they are not authorized to receive.
Another solution to the secure transmission of information signals in point-to-point systems is a "space division" system. In such systems, individual wires are employed to carry each session. The only signal present on the individual line is the one destined for the end node connected to that line. Users at other end nodes do not have access to transmissions that they are not authorized to receive.
Space division systems have the drawback that they are expensive to establish and maintain. A separate wired path must be provided from the headend to each individual subscriber. The cost of installing and maintaining such individual paths is prohibitive.
Known encryption systems are not optimal for point-to-point communications over shared media. In particular, such known encryption systems require the secure handling of the session keys. This places an added burden on the system operators that control the various headend sites at which the signal distribution to individual subscribers originates.
It would be advantageous to provide a point-to-point security scheme that allows "common keys" to be used for all sessions within the network. Common keys are keys which are used across a population of different subscribers. The common keys are changed periodically, e.g., monthly, and the same keys are distributed to different subscribers. Such common keys are disseminated far in advance of the establishment of any particular communication session, in which information is provided from the headend to an individual subscriber. The advantageous use of common keys would allow the information required to establish a secure session to be handled with a lower level of security than in the past. An advantageous result would be that a managing entity, such as a connection management system, would be able to establish session security without handling secure information. By eliminating the requirement that the managing entity handle secure information, the cost of the associated secure hardware and software as well as the cost burden of handling secure information would be saved.
The present invention provides a data security scheme for a point-to-point communication system having the aforementioned advantages. More particularly, the present invention takes the handling of secure information out of the hands of the connection management system or other managing entity, and places it in a centralized "encryption controller" that may be maintained in a hardened bunker or other secure area for communication with the signal switching and distribution components of the system on an "as needed" basis; e.g., for system configuration. Once the connection management system has been configured, the encryption controller is not required to participate in the actual set up of individual sessions.